Rear master cylinder help

You sure that will work for the rear? Ad says front.

Sardonicus wrote: You sure that will work for the rear? Ad says front.

Your right, I didn't catch that :blush:
Pete

No worries - I've got emails out to a few sites that sell parts to see if they can shed a ray of hope on my plight.

If I can't find the parts and have to figure something else out can you tell me how important it is that the bore size is the same? I'm sure I can mount just about any master cylinder I can get my hands on where this one is suppose to be. Where there's a welder there's a way. Just want to be sure it will still be capable of doing the job.

pete greek1 wrote: The rear master cylinder piston for a 76 KZ 750 twin, part # 43072-004
is used on these models
1976 KZ750-B1 REAR MASTER CYLINDER-BRAKE PEDAL

1976 KZ900-B1 LTD REAR MASTER CYLINDER

1977 KZ1000-A1 KZ1000 REAR MASTER CYLINDER(KZ1000-A3-A3A)

1977 KZ1000-A1 KZ1000 REAR MASTER CYLINDER-BRAKE PEDAL ('77-'7

1977 KZ1000-B1 KZ1000 LTD REAR MASTER CYLINDER-BRAKE PEDAL ('77-'7

1977 KZ1000-B1 KZ1000 LTD REAR MASTER CYLINDER-BRAKE PEDAL (KZ1000

1977 KZ750-B2 REAR MASTER CYLINDER-BRAKE PEDAL

<snip>
Pete

I too need to rebuild the rear MC on my KZ750B1 Twin. Does this list of compatible pistons mean that a rebuild kit for one of these models should work for my bike (springs, seals, circlips etc.)?

To that I would say more than likely yes. Once you have yours apart compare your parts to any kit you find. Mine was seized but I got it apart today and it pains me to say if I hadn't damaged the piston it would have been fine.

Cool, thanks

Bowman wrote:

pete greek1 wrote: The rear master cylinder piston for a 76 KZ 750 twin, part # 43072-004
is used on these models
1976 KZ750-B1 REAR MASTER CYLINDER-BRAKE PEDAL

1976 KZ900-B1 LTD REAR MASTER CYLINDER

1977 KZ1000-A1 KZ1000 REAR MASTER CYLINDER(KZ1000-A3-A3A)

1977 KZ1000-A1 KZ1000 REAR MASTER CYLINDER-BRAKE PEDAL ('77-'7

1977 KZ1000-B1 KZ1000 LTD REAR MASTER CYLINDER-BRAKE PEDAL ('77-'7

1977 KZ1000-B1 KZ1000 LTD REAR MASTER CYLINDER-BRAKE PEDAL (KZ1000

1977 KZ750-B2 REAR MASTER CYLINDER-BRAKE PEDAL

<snip>
Pete

I too need to rebuild the rear MC on my KZ750B1 Twin. Does this list of compatible pistons mean that a rebuild kit for one of these models should work for my bike (springs, seals, circlips etc.)?

Those models use the same piston for the FRONT master cylinders, I think the rears would be different , front M/C piston part # is
43072-001, & the rear piston # is 43072-004
Pete

Now that I have mine apart and have had a chance to inspect some of the parts I can say with relative certainty that this kit
www.z1enterprises.com/product/KZ1000MCKIT1
Will have the correct parts to rebuild the rear master cylinder. This whole ordeal has been a very interesting learning experience and now that I know how to unseize these master cylinders without breaking anything I find that if I had just done it right the first time I wouldn't actually need to be buying any parts at all. Aside from the part of the piston I damaged everything is fine - it was just stuck. The other cup is fine and the spring is still quite springy. So far the only major difference I have noticed between this kit and the parts that I have is that this kit comes with a spring clip instead of a snap ring.

I am new to motorcycles so what I am learning may be things that are common knowledge for people familiar with motorcycles but in the off chance that anyone else wants to know an easy way to push out a stuck piston let me know and I will tell you how I did it.

The 1st key to searching for the right replacement parts on any bike that is new to you (especially these older ones) is making sure whether or not the specific needed parts are original to that model. Over the years some parts get swapped around here and there by previous owners for whatever reason and can sometimes make finding the actual parts you need a nightmarish endeavor. Pics can also help when inquiring about advice on forums like this, as many readers can spot oddball or unique parts just by seeing them and be of better assistance from their own similar experiences. Good luck ........................................Mike

Vroom-vroom!!!

and now that I know how to unseize these master cylinders without breaking anything

What's your technique?
I've got a few to work on.

Friend of mine suggested screwing a grease fitting into the port on the master cylinder that the line going to the caliper would screw into and then attach a grease gun to it. Good grease guns can put out some crazy high pressure and with just a few pumps the piston slides right out. Seems like the spring catches most of the grease. Clean out with kerosene or something similar and you're good.

Happy to say upon receiving the donor master cylinder in the mail I was able to get everything together and the rear brakes are now fully functional. I'll probably put the other master cylinder on eBay or something with the primary cup and spring. Probably recoup most of what I spent to make this one work.